1. Technical Field
The present invention relates to a device, a test apparatus, and a test method.
2. Related Art
When testing a device, if a signal is supplied from an external unit to an arbitrary circuit point of the device or if a signal is acquired by an external unit from an arbitrary circuit point of the device, it is necessary to provide the device with an external terminal for testing and signal lines providing a connection between the external terminal and arbitrary points in the circuit. Therefore, if a signal must be acquired or supplied at many circuit points in the device during testing, the device must be provided with many external terminals. This causes an undesirable increase in the circuit size of the device.
U.S. Pat. No. 5,659,312 discloses a device provided with an internal DA converter and AD converter for testing. Japanese Patent Application Publication No. 03-284862 discloses a semiconductor apparatus in which a plurality of analog circuits under test are connected to a single test terminal via an analog switch. Both of these inventions decrease the number of external terminals used for testing.
Japanese Patent Application Publication No. 2002-236151 discloses an auxiliary apparatus that causes the output of the DA converter in the circuit under test to loop-back to the AD converter in the circuit under test via an external circuit under test, thereby enabling the circuit under test to perform a self-test. Since the loop-back line is formed outside of the circuit under test, this invention enables accurate testing, because the loop-back line has low distortion.
However, the device disclosed in U.S. Pat. No. 5,659,312 requires that a DA converter and AD converter be disposed inside the device, which leads to higher cost. Furthermore, measurement accuracy of this device is limited by the capabilities of the AD converter and the DA converter, making it difficult to achieve accurate testing.
The semiconductor apparatus described above creates signal distortion due to the analog switch, and therefore it is difficult to perform accurate measuring. Finally, with the auxiliary device described above, it is difficult to measure arbitrary circuit points in the device under test.